A device for improving the utilization rate of carbonate methanol and a process method thereof

Abstract

This invention discloses a device and process for improving methanol utilization in carbonate production, belonging to the field of carbonate production technology. Dimethyl carbonate and ethanol are introduced into a reaction tower and reacted under the action of catalyst a to produce ethyl methyl carbonate, diethyl carbonate, and methanol as a byproduct. The atmospheric pressure azeotrope is distilled off from the top of the reaction tower and enters a pressurized tower for separation. Another atmospheric pressure azeotrope, with a mass ratio of dimethyl carbonate to methanol of 1:2.3-3.3, distilled off from the DMC reaction tower, also enters the pressurized tower. The ratio of dimethyl carbonate to methanol azeotrope is changed by increasing the operating pressure. Dimethyl carbonate collected from the bottom of the pressurized tower is sent to the EMC reaction tower as a raw material using pressure differential. The pressurized azeotrope, with a mass ratio of dimethyl carbonate to methanol of 1:8-9.5, distilled off from the top of the pressurized tower, is sent to the DMC reaction tower as a raw material. This invention solves the technical problem of low methanol utilization in existing processes and is mainly applied to carbonate production.

Description

Technical Field

[0001] The invention relates to the technical field of carbonate integrated production, and in particular to a device for improving the methanol utilization rate of a carbonate device and a process method thereof. Background Art

[0002] Lithium battery electrolyte is the carrier of ion transmission in the battery. It is generally composed of lithium salt and organic solvent. The electrolyte is generally prepared under certain conditions and in a certain proportion from high-purity organic solvent, electrolyte lithium salt, necessary additives and other raw materials. The raw materials of commonly used solvents for lithium battery electrolyte are: ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc.

[0003] At present, most newly built integrated carbonate projects use the ethylene oxide route to produce carbonate products, that is, ethylene oxide and carbon dioxide are reacted to generate ethylene carbonate, ethylene carbonate and methanol are reacted to generate dimethyl carbonate, and dimethyl carbonate and ethanol are reacted to generate ethyl methyl carbonate and diethyl carbonate. In the process of producing electronic-grade products, the grade requirements for raw materials are relatively high. For example, methanol and ethanol both need to be of superior grade or above. In the process of producing ethyl methyl carbonate, due to the conversion rate problem, the raw material dimethyl carbonate and the by-product methanol will form an azeotrope, and the separation of the azeotrope requires high energy consumption. At present, the mainstream processes for separating the azeotrope formed by methanol and dimethyl carbonate in the industry are: low-temperature crystallization, extractive distillation, pressure distillation, and membrane separation. For the ethylene oxide route, the current mature and reliable process is the pressure distillation method. Since the azeotrope contains various trace compounds in the process of producing ethyl methyl carbonate, such as ethanol, ethyl methyl carbonate, diethyl carbonate and catalyst, methanol and dimethyl carbonate will contain some trace components in the separation process of the azeotrope. If the product is to be purified, it is necessary to add separation equipment, which will increase production costs. Since dimethyl carbonate has a high added value, adding purification equipment can greatly increase profits; but the added value of methanol is relatively low, and purifying this product will significantly increase production costs.

[0004] In summary, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, as excellent electrolyte solvents for lithium-ion batteries, have broad market prospects, but there are problems of consuming high-purity raw material methanol and producing low-grade methanol as a by-product, which is an economic loss for enterprises. In order to survive by quality and reduce costs by technology, the overall economic benefits can be improved, so we need a process control method to improve the utilization rate of methanol. Summary of the invention

[0005] In view of the shortcomings of the existing process technology, the present invention provides a carbonate methanol utilization rate improvement device and a process method thereof, which improves the utilization rate of methanol and increases the output of high value-added products by reusing the methanol generated by the reaction. The specific scheme is as follows:

[0006] A device for improving the utilization rate of carbonate methanol comprises a DMC reaction tower, a condenser a, a reflux tank a and a circulation pump a, wherein the DMC reaction tower is connected with the condenser a through a pipeline, the condenser a is connected with the reflux tank a through a pipeline, the reflux tank a is connected with the circulation pump a through a pipeline, the circulation pump a is connected with the DMC reaction tower through a pipeline, and the lower part of the DMC reaction tower is connected with a heater a.

[0007] The core improvement of the present invention is to connect the circulating pump a with the pressurizing tower through a pipeline, the lower part of the pressurizing tower is provided with a heater b, the upper part of the pressurizing tower is connected with the condenser b through a pipeline, the condenser b is connected with the reflux tank b through a pipeline, the reflux tank b is connected with the circulating pump b through a pipeline, the circulating pump b is connected with the pressurizing tower and the DMC reaction tower through pipelines, the lower part of the pressurizing tower is connected with the EMC reaction tower through a pipeline, the lower part of the EMC reaction tower is connected with the heater c, the upper part of the EMC reaction tower is connected with the condenser c through a pipeline, the condenser c is connected with the reflux tank c through a pipeline, the lower part of the reflux tank c is connected with the circulating pump c through a pipeline, and the circulating pump c is connected with the EMC reaction tower and the pressurizing tower through pipelines.

[0008] The process flow of the above equipment mainly includes the following steps:

[0009] Step 1: Dimethyl carbonate and ethanol enter the EMC reaction tower to react, and react under the action of catalyst a to generate product ethyl methyl carbonate, diethyl carbonate and by-product methanol. The specific reaction is as follows:

[0010] First, dimethyl carbonate and ethanol react to produce ethyl methyl carbonate and methanol. The equation is as follows:

[0011]

[0012] Ethyl methyl carbonate then reacts with ethanol to form diethyl carbonate and methanol. The equation is as follows:

[0013]

[0014] The crude products of ethyl methyl carbonate and diethyl carbonate are sent from the bottom of the EMC reaction tower to the downstream distillation unit for separation, and then the products of ethyl methyl carbonate and diethyl carbonate are obtained;

[0015] The atmospheric azeotrope formed by the unreacted dimethyl carbonate and the byproduct methanol in the EMC reaction tower with a mass ratio of 1:2.3-3.3 is evaporated from the top of the EMC reaction tower and enters the pressure tower for separation;

[0016] Step 2: The dimethyl carbonate that did not participate in the reaction in step 1 forms an atmospheric azeotrope with the byproduct methanol in a mass ratio of 1:2.3-3.3 and enters the pressure tower, and another atmospheric azeotrope with a mass ratio of 1:2.3-3.3 between the product dimethyl carbonate distilled from the DMC reaction tower and the raw material methanol also enters the pressure tower, and the ratio of the dimethyl carbonate and methanol azeotrope is changed by increasing the operating pressure; the dimethyl carbonate extracted from the bottom of the pressure tower is sent to the EMC reaction tower as a raw material by pressure difference; the pressurized azeotrope with a mass ratio of 1:8-9.5 between the dimethyl carbonate distilled from the top of the pressure tower and the raw material methanol is sent to the DMC reaction tower as a raw material;

[0017] Step 3: The pressurized azeotrope of dimethyl carbonate and methanol in a mass ratio of about 1:8.5-9.5 distilled from the top of the pressure tower in step 2 and the raw material ethylene carbonate enter the DMC reaction tower to react under the action of catalyst b to generate dimethyl carbonate and ethylene glycol. The crude ethylene glycol is sent from the bottom of the DMC reaction tower to the downstream distillation unit for purification to obtain an ethylene glycol product; the atmospheric pressure azeotrope of dimethyl carbonate and raw material methanol in a mass ratio of 1:2.3~3.3 is evaporated from the top of the tower and enters the pressure tower for separation. The reaction principle of this step is:

[0018] Ethylene carbonate and methanol react to produce dimethyl carbonate and ethylene glycol, the equation is as follows:

[0019]

[0020] Preferably, the catalyst a in step 1 is one or more of potassium carbonate, sodium methoxide methanol solution, a novel ionic liquid catalyst, and an alkaline solid-supported catalyst.

[0021] Preferably: the top temperature of the EMC reaction tower is controlled at 60-70°C, the kettle temperature of the EMC reaction tower is controlled at 90-110°C, the pressure is normal pressure, and the reflux ratio is controlled at 2-4. Under this operating condition, the raw material conversion rate can be improved, the separation effect of the tower can be improved, and the comprehensive utilization rate of methanol can be improved.

[0022] Preferably: the top temperature of the pressure tower 2 in step 2 is controlled at 150-180° C., the bottom temperature is controlled at 200-240° C., the pressure is controlled at 1.5-2.5 MPa, and the reflux ratio is controlled at 1-3. Under the operating conditions, the methanol content in the pressurized azeotrope extracted from the top of the pressure tower is very high, and the dimethyl carbonate content is low, which can improve the utilization rate of methanol and reduce the repeated circulation of dimethyl carbonate between the DMC reaction tower and the pressure tower as much as possible; the crude dimethyl carbonate extracted from the bottom of the pressure tower has very little methanol content and can directly participate in the reaction of the EMC reaction tower without excessive refining.

[0023] Preferably: in step 3, the top temperature of the DMC reaction tower 1 is controlled at 60-70°C, the bottom temperature is controlled at 70-90°C, the pressure is normal pressure, and the reflux ratio is controlled at 2-4. Under this operating condition, the raw material conversion rate can be improved, the separation effect of the tower can be improved, and the separation of dimethyl carbonate can be facilitated.

[0024] Preferably: the catalyst b in step three is one or more of sodium methoxide methanol solution and alkaline solid catalyst. Preferably: the operating pressure of step one and step three is slightly positive pressure, and the operating pressure of step two is above 1.0 MPa. The more preferred solution is that the operating pressure of step two is above 2.0 MPa.

[0025] Preferably, the methanol of the atmospheric azeotrope generated in step 1 is directly used as a raw material in step 3 after simple separation in step 2, without excessive purification of the methanol, which can reduce product energy consumption and enhance market competitiveness.

[0026] Preferably, the crude dimethyl carbonate separated in step 2 is directly used as a raw material in step 1 without excessive purification, and does not affect the quality of the high value-added product ethyl methyl carbonate.

[0027] Preferably: the present invention can increase the output of high value-added methyl ethyl carbonate by increasing the raw materials methanol, ethanol, and ethylene carbonate, or increasing the raw materials dimethyl carbonate and ethanol, or adjusting the ratio of the raw materials methanol, ethanol, ethylene carbonate, and dimethyl carbonate according to market conditions.

[0028] The beneficial effects of the present invention are:

[0029] 1) The present invention couples the DMC reaction tower system, the pressurized tower system, and the EMC reaction tower system together, so that the byproduct methanol generated by the EMC reaction tower system can be completely consumed in the DMC reaction tower system, without considering the purification of the byproduct methanol, thereby reducing the energy input for low value-added products, thereby achieving the effect of saving production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a structural diagram of the device of the present invention.

[0031] In the figure: 1. DMC reaction tower; 1-1 condenser a; 1-2 reflux tank a; 1-3 reflux pump a; 1-4 heater a; 2. Pressurization tower; 2-1 condenser b; 2-2 reflux tank b; 2-3 reflux pump b; 2-4 heater b; 3. EMC reaction tower; 3-1 condenser c; 3-2 reflux tank c; 3-3 reflux pump c; 3-4 heater c. DETAILED DESCRIPTION Embodiment 1:

[0032] like Figure 1 As shown:

[0033] The raw material supplementary methanol, raw material ethylene carbonate and a suitable catalyst are added to the DMC reaction tower 1 in a certain proportion, the tower top temperature is controlled at 60-70°C, the tower bottom temperature is controlled at 70-90°C, the pressure is normal pressure, and the reflux ratio is controlled at 2, and dimethyl carbonate and ethylene glycol are generated by the reaction. The crude ethylene glycol is sent from the bottom of the DMC reaction tower 1 to the downstream distillation unit for purification to obtain an ethylene glycol product; the atmospheric pressure azeotrope formed by the reaction and the raw material methanol in a mass ratio of 1:2.3 is evaporated from the tower top and enters the pressure tower 2 for separation;

[0034] The top temperature of pressure tower 2 is controlled at 150-180°C, the bottom temperature is controlled at 200-240°C, the pressure is controlled at 2.5MPa, and the reflux ratio is controlled at 1-3; the pressurized azeotrope of dimethyl carbonate evaporated from the top of pressure tower 2 and raw material methanol in a mass ratio of 1:9 is sent to DMC reaction tower 1 as raw material to consume unreacted methanol; the dimethyl carbonate extracted from the bottom of pressure tower 2 is sent to EMC reaction tower 3 as raw material by pressure difference.

[0035] The dimethyl carbonate, raw material ethanol and a suitable catalyst are taken out from the bottom of the pressure tower 2 and enter the EMC reaction tower 3 in appropriate proportions. The top temperature of the tower is controlled at 60-70°C, the bottom temperature is controlled at 90-110°C, the pressure is normal pressure, the reflux ratio is 3, and the crude products of ethyl methyl carbonate and diethyl carbonate are sent from the bottom of the tower to the downstream distillation unit for separation to obtain products of ethyl methyl carbonate and diethyl carbonate; the atmospheric pressure azeotrope formed by the dimethyl carbonate that does not participate in the reaction and the by-product methanol in a mass ratio of 1:2.3 is evaporated from the top of the tower and enters the pressure tower 2 for separation.

[0036] The ratio of raw material ethylene carbonate, supplementary methanol and ethanol is adjusted according to market conditions so that the final products only have high value-added ethyl methyl carbonate, diethyl carbonate and ethylene glycol, without low-grade methanol products. Embodiment 2:

[0037] like Figure 1 As shown:

[0038] The raw materials of supplementary dimethyl carbonate, ethanol and a suitable catalyst are fed into the EMC reaction tower 3 in appropriate proportions, the tower top temperature is controlled at 60-70°C, the tower bottom temperature is controlled at 90-110°C, the pressure is normal pressure, the reflux ratio is controlled at 2, and the crude products of ethyl methyl carbonate and diethyl carbonate are sent from the tower bottom to the downstream distillation unit for separation to obtain products of ethyl methyl carbonate and diethyl carbonate; the atmospheric pressure azeotrope formed by the dimethyl carbonate which does not participate in the reaction and the by-product methanol in a mass ratio of 1:3.3 is evaporated from the tower top and fed into the pressurized tower 2 for separation.

[0039] The top temperature of pressure tower 2 is controlled at 150-180°C, the bottom temperature is controlled at 200-240°C, the pressure is controlled at 1.5MPa, the reflux ratio is controlled at 1, and the pressurized azeotrope with a mass ratio of dimethyl carbonate and raw material methanol of 1:9 evaporated from the top of pressure tower 2 is sent to DMC reaction tower 1 as raw material to consume unreacted methanol again; the dimethyl carbonate extracted from the bottom of pressure tower 2 is sent to EMC reaction tower 3 as raw material by pressure difference.

[0040] The pressurized azeotrope of dimethyl carbonate and methanol in a mass ratio of 1:9 dimethyl carbonate and methanol distilled from the top of the pressure tower 2, ethylene carbonate and a suitable catalyst enter the DMC reaction tower 1 in a suitable proportion, the top temperature is controlled at 60-70°C, the bottom temperature is controlled at 70-90°C, the pressure is normal pressure, the reflux ratio is controlled at 4, and the reaction generates dimethyl carbonate and ethylene glycol. The crude ethylene glycol is sent from the bottom of the DMC reaction tower 1 to the downstream distillation unit for purification to obtain an ethylene glycol product; the atmospheric pressure azeotrope of dimethyl carbonate and raw material methanol in a mass ratio of 1:3.3 dimethyl carbonate generated by the reaction and the raw material methanol is distilled from the top of the tower and enters the pressure tower 2 for separation;

[0041] The proportions of the raw materials ethylene carbonate, dimethyl carbonate and ethanol are adjusted according to market conditions so that the final products only have high value-added ethyl methyl carbonate, diethyl carbonate and ethylene glycol, without low-grade methanol products. Embodiment 3:

[0042] like Figure 1 As shown:

[0043] The raw material supplementary methanol, raw material ethylene carbonate and a suitable catalyst are added to the DMC reaction tower 1 in a certain proportion, and the tower top temperature is controlled at 60-70°C, the tower bottom temperature is controlled at 70-90°C, the pressure is normal pressure, and the reflux ratio is 3. The reaction generates dimethyl carbonate and ethylene glycol, and the crude ethylene glycol is sent from the tower bottom of the DMC reaction tower 1 to the downstream distillation unit for purification to obtain the ethylene glycol product; the atmospheric pressure azeotrope formed by the reaction with the raw material methanol in a mass ratio of 1:3 is evaporated from the tower top and enters the pressure tower 2 for separation.

[0044] The top temperature of the pressure tower 2 is controlled at 150-180°C, the bottom temperature is controlled at 200-240°C, the pressure is controlled at 2MPa, and the reflux ratio is controlled at 3. The pressurized azeotrope of dimethyl carbonate and raw material methanol in a mass ratio of 1:8.5 dimethyl carbonate distilled from the top of the pressure tower 2 is sent to the DMC reaction tower 1 as a raw material to consume unreacted methanol; the dimethyl carbonate produced from the bottom of the pressure tower 2 is sent to the EMC reaction tower 3 as a raw material by pressure difference.

[0045] The dimethyl carbonate extracted from the bottom of the pressure tower 2, the raw material supplementary dimethyl carbonate, the raw material ethanol and the appropriate catalyst are fed into the EMC reaction tower 3 in appropriate proportions, the tower top temperature is controlled at 60-70°C, the tower bottom temperature is controlled at 90-110°C, the pressure is normal pressure, and the reflux ratio is controlled at 3. The crude products of ethyl methyl carbonate and diethyl carbonate are sent from the bottom of the tower to the downstream distillation unit for separation to obtain the products of ethyl methyl carbonate and diethyl carbonate; the atmospheric pressure azeotrope formed by the unreacted dimethyl carbonate and the by-product methanol in a mass ratio of 1:3 is evaporated from the top of the tower and enters the pressure tower for separation.

[0046] The proportions of the raw materials ethylene carbonate, dimethyl carbonate, methanol and ethanol are adjusted according to market conditions so that the final products only contain high value-added ethyl methyl carbonate, diethyl carbonate and ethylene glycol, without low-grade methanol products.

[0047] The above description is only a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements without departing from the principle of the present invention. These improvements should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for using a carbonate methanol utilization rate improving device, the device comprising a DMC reaction tower (1), a condenser a (1-1), a reflux tank a (1-2) and a circulation pump a (1-3), the DMC reaction tower (1) being connected to the condenser a (1-1) via a pipeline, the condenser a (1-1) being connected to the reflux tank a (1-2) via a pipeline, the reflux tank a (1-2) being connected to the circulation pump a (1-3) via a pipeline, the circulation pump a (1-3) being connected to the DMC reaction tower (1) via a pipeline, and the lower part of the DMC reaction tower (1) being connected to a heater a (1-4); The circulating pump a (1-3) is connected to the pressure tower (2) through a pipeline, the lower part of the pressure tower (2) is provided with a heater b (2-4), the upper part of the pressure tower (2) is connected to the condenser b (2-1) through a pipeline, the condenser b (2-1) is connected to the reflux tank b (2-2) through a pipeline, the reflux tank b (2-2) is connected to the circulating pump b (2-3) through a pipeline, the circulating pump b (2-3) is connected to the pressure tower (2) and the DMC reaction tower (1) through pipelines, respectively, the lower part of the pressure tower (2) is connected to the condenser b (2-1) through a pipeline, the condenser b (2-1) is connected to the reflux tank b (2-2) through a pipeline, the reflux tank b (2-2) is connected to the circulating pump b (2-3) through pipelines, the circulating pump b (2-3) is connected to the pressure tower (2) and the DMC reaction tower (1) through pipelines, and the lower part of the pressure tower (2) is connected to the condenser b (2-1) through a pipeline. The upper part of the EMC reaction tower (3) is connected to the condenser c (3-1) through a pipeline, the condenser c (3-1) is connected to the reflux tank c (3-2) through a pipeline, the lower part of the reflux tank c (3-2) is connected to the circulation pump c (3-3) through a pipeline, and the circulation pump c (3-3) is respectively connected to the EMC reaction tower (3) and the pressure tower (2) through pipelines, characterized in that: The following steps are involved: Step 1: Dimethyl carbonate and ethanol enter the EMC reaction tower (3) for reaction. Under the action of catalyst a, the reaction generates product ethyl methyl carbonate, diethyl carbonate and by-product methanol. The specific reaction is as follows: First, dimethyl carbonate and ethanol react to produce ethyl methyl carbonate and methanol. The equation is as follows: ； Ethyl methyl carbonate then reacts with ethanol to form diethyl carbonate and methanol. The equation is as follows: ； The crude products of ethyl methyl carbonate and diethyl carbonate are sent from the bottom of the EMC reaction tower (3) to a downstream distillation unit for separation, and then the products of ethyl methyl carbonate and diethyl carbonate are obtained; The atmospheric pressure azeotrope formed by the unreacted dimethyl carbonate and the by-product methanol in the EMC reaction tower (3) with a mass ratio of 1:2.3-3.3 is evaporated from the top of the EMC reaction tower (3) and enters the pressure tower (2) for separation; Step 2: the dimethyl carbonate that did not participate in the reaction in step 1 forms an atmospheric azeotrope with the byproduct methanol in a mass ratio of 1:2.3-3.3 and enters the pressure tower (2); another atmospheric azeotrope with a mass ratio of 1:2.3-3.3 between the product dimethyl carbonate distilled from the DMC reaction tower (1) and the raw material methanol also enters the pressure tower (2), and the ratio of the dimethyl carbonate and methanol azeotrope is changed by increasing the operating pressure; the dimethyl carbonate extracted from the bottom of the pressure tower (2) is sent to the EMC reaction tower (3) as a raw material by pressure difference; the pressurized azeotrope with a mass ratio of 1:8-9.5 between the dimethyl carbonate distilled from the top of the pressure tower (2) and the raw material methanol is sent to the DMC reaction tower (1) as a raw material; Step 3: The pressurized azeotrope of dimethyl carbonate and methanol in a mass ratio of 1:8.5-9.5 distilled from the top of the pressure tower (2) in step 2 and the raw material ethylene carbonate enter the DMC reaction tower (1) to react under the action of catalyst b to generate dimethyl carbonate and ethylene glycol. The crude ethylene glycol product is sent from the bottom of the DMC reaction tower (1) to the downstream distillation unit for purification to obtain an ethylene glycol product; the atmospheric pressure azeotrope of dimethyl carbonate and raw material methanol in a mass ratio of 1:2.3-3.3 distilled from the top of the tower and enters the pressure tower (2) for separation. The reaction principle of this step is: Ethylene carbonate and methanol react to produce dimethyl carbonate and ethylene glycol, the equation is as follows: 。 2. The method for using the carbonate methanol utilization rate improving device according to claim 1, characterized in that: The top temperature of the EMC reaction tower (3) is controlled at 60-70°C, the bottom temperature of the EMC reaction tower (3) is controlled at 90-110°C, the pressure is normal pressure, and the reflux ratio is controlled at 2-4.

3. The method for using the carbonate methanol utilization rate improving device according to claim 1, characterized in that: In the step 2, the top temperature of the pressure tower (2) is controlled at 150-180° C., the bottom temperature is controlled at 200-240° C., the pressure is controlled at 1.5-2.5 MPa, and the reflux ratio is controlled at 1-3.

4. The method for using the carbonate methanol utilization rate improving device according to claim 1, characterized in that: In the step 3, the top temperature of the DMC reaction tower (1) is controlled at 60-70°C, the bottom temperature is controlled at 70-90°C, the pressure is normal pressure, and the reflux ratio is controlled at 2-4.

5. The method for using the carbonate methanol utilization rate improving device according to claim 1, characterized in that: The operating pressures of step 1 and step 3 are slightly positive, and the operating pressure of step 2 is above 1.0 MPa.

6. The method for using the carbonate methanol utilization rate improving device according to claim 5, characterized in that: The operating pressure of step 2 is 2.0 MPa.

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